The proposed research plan involves the investigation of the nature of ligand induced conformation changes in multi-subunit enzymes which alter the catalytic activity. This study can effectively serve as a model for many of the dynamic processes in biology which are mediated and controlled through conformation changes in proteins. The work with glyceraldehyde-3-phosphate dehydrogenase will be in three general areas. A) The mechanism of action will be studied by steady-state and transient kinetics and with phosphate and aldehyde analogs. The effects of these analogs on chemical reactivity and cooperativity will be analyzed. The effect of covalent modification of the enzyme with substrate and transition state analogs on the alteration of the NAD binding cooperativity pattern will also be studied. B) The catalytic role of NAD will be investigated, particularly with regards to the alteration in specificity towards the acceptor in the deacylation of the thiol-ester intermediate. () Inhibition studies will be carried out to investigate the effects of substituents on intersubunit interactions and the relationship between binding energy and catalytic energy. Transition state analogs will be used to determine the transition state structure and the conformation changes which occur in the act of catalysis. Chemical and inhibition studies with palmitoyl-CoA synthetase will be carried out to further analyze the role of subunit interactions in a biochemical energy transducing system.